[Matplotlib-users] Key Press and Key Release Events in TkInter

[Gregory Key]

Bingo! Searching for 'key debounce in tkinter' was what I needed. I
think I have found a solution. Thanks!

Greg Key

On Thu, 2017-02-02 at 21:35 +0000, Gregory Key wrote:
> So basically in tkinter the key_release_event is useless.
> 
> Thanks I'll do some experimenting with the information you have given
> me.
> 
> On Thu, 2017-02-02 at 14:07 -0600, Joe Kington wrote:
> > That's a common "gotcha" when trying to detect a held key on a
> > keyboard.  Your operating system (or the actual hardware in your
> > keyboard in some cases) interprets a held key as multiple
> > keypresses
> > and fires off events accordingly (e.g., that's why holding down "a"
> > will give "aaaaaaaaa" when typing).
> > 
> > I think Qt handles this automatically, but I could be wrong. Tk
> > doesn't do it automatically.
> > 
> > Usually, you'd detect a held key by keeping track of the either the
> > last key press event or the time since the last keypress event.
> >  "Debouncing" is the term you'll want to search for.  In tkinter,
> > you
> > can bind a function to fire after idle (effectively checking if the
> > key was ever released).  Alternatively, for the matplotlib side, I
> > think you can bind to the idle event and do the same thing without
> > needing to rely on anything tkinter-specific (Untested).
> > 
> > Hope that helps a bit, anyway.
> > -Joe
> > 
> > On Tue, Jan 31, 2017 at 3:05 PM, Gregory Key <gregk3172 at outlook.com
> > >
> > wrote:
> > > I am running Python 3.5.2 and MatPlotLib 2.0.0 on Ubuntu 16.10.
> > > 
> > > I am developing a program that uses matplotlib embedded in
> > > tkinter
> > > to
> > > plot vibration data in a bode plot, phase and amplitude versus
> > > rotor
> > > speed. I adapted the data browser given in the matplotlib
> > > documentation
> > >             as example 91.2 data_browser.py to browse the data.
> > > The
> > > browser worked but I wanted to modify it so that holding down the
> > > next
> > > or previous key would scroll through the data instead of having
> > > to
> > > continously press and release the keys. My plan was to use the
> > > key_press_event to start a timer which would call a scroll method
> > > and
> > > then use the key_release event to stop the timer and stop
> > > scrolling. I
> > > couldn't make this scheme work so I did some investigating on the
> > > key_press_event and key_release_event in tkinter. I used example
> > > 91.5
> > > keypress_demo.py given in the matplotlib documentation but I
> > > added
> > > a
> > > key_release_event method to it. What I found was that the key
> > > events
> > > don't work the way I would expect them to work. If you press and
> > > release a key things work as expected. When a key is pressed the
> > > key_press_event fires and when it is released the
> > > key_release_event
> > > fires. If a key is pressed and held however the key_press_event
> > > fires
> > > followed immediately by a key_release_event even though the key
> > > has
> > > not
> > > been released. As long as the key is held down it will continue
> > > to
> > > fire
> > > key_press_event followed by key_release_event. Is this the way it
> > > is
> > > supposed to work?
> > > 
> > > Thanks
> > > Greg Key
> > > _______________________________________________
> > > Matplotlib-users mailing list
> > > Matplotlib-users at python.org
> > > https://mail.python.org/mailman/listinfo/matplotlib-users
> > > 
> > 
> > 
> 
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